NO155585B - PROCEDURE FOR DELIGNIFICATION OF LIGNOCELLULOS MATERIALS. - Google Patents

Abstract

A process for delignifying lignocellulosic material with a digestion liquor of nitroanthraquinones and/or dinitroanthraquinones. The process can be carried out in a closed reaction vessel at temperatures of 150 DEG -200 DEG +/- C. for 0.5 to 480 minutes with 0.001 to 10% nitroanthraquinone and/or dinitroanthraquinone by weight of lignocellulosic material.

Description

The invention relates to a method for de-lignifying lignocellulosic materials with the addition of nitroanthraquinone compounds.

In Swedish Papperstidning 71, pp. 857-863 (1968) it is mentioned that nitrobenzene and nitrobenzoic acid have an inhibitory effect on the alkaline chain shortening reaction during delignification. In the same literature, it is stated that this realization has not resulted in any technical application.

The invention relates to a method for de-lignifying lignocellulosic materials by digesting lignocellulosic materials with ordinary cooking liquids, preferably an alkaline cooking liquid, under ordinary cooking conditions in the presence of aromatic nitro compounds, the method being characterized in that one or more nitroanthraquinone compounds are used as the aromatic nitro compound in a amount of 0.01-1% by weight, referred to lignocellulosic material used.

With the method according to the invention, the most diverse lignocellulosic materials can be delignified. For example, conifers such as spruce, pine and Norway spruce are suitable

and deciduous trees such as beech, birch, eucalyptus, aspen, poplar, willow, white beech, alder, oak and maple and straw and bagasse an annual plants. Fir, pine, Norway spruce, birch and beech are preferably delignified by the method according to the invention,

In the method according to the invention for delignification of lignocellulosic materials, one or more nitroanthraquinone compounds are added to the cooking liquid.

One of the usual cooking liquids can be used as cooking liquid

for alkaline boiling processes or sulphite processes or similar processes. The term "alkaline cooking methods" includes various methods, e.g. the soda process, the sulfate process, the polysulfide process, etc., and the term "sulfite process" used here includes different processes, for example the alkaline, neutral and acidic sulfite process, the bisulfite process, etc. (pp. P. Lengyel, S. Morvay, Chemie und Technologie der Zellstoffherstellung, Guntter-

Staib Verlag, Biberach/Riss, 1973, pages 62 et seq.).

For example, you can carry out the procedure

according to the invention in a closed reaction vessel in which the lignocellulose material is treated with the cooking liquid at maximum temperatures in the range from 150 to 200°C, preferably from 160 to 180°C over a period of time from 0.5 to 480 minutes, preferably from 15 to 200 minutes.

After this digestion treatment, the de-lignified material can be processed in the usual way, for example by displacing the cooking liquid from the lignocellulosic material by adding water or an aqueous liquid inert to the lignocellulosic material. The thus processed and possibly additionally mechanically phased lignocellulose material can be used without further treatment or subjected to normal bleaching procedures.

Alternatively, the delignified lignocellulosic material can be further processed as follows: The material is treated in an aqueous suspension whose content of lignocellulosic materials is 2 to 40% by weight, for 0.5 to 60 minutes at 20 to 90°C with 2 to 20% by weight # of an alkali metal base and optionally then with oxygen or an oxygen-containing gas for 0.5 to 120 minutes at a temperature of 80 to 150°C and an oxygen partial pressure of 1.4 to 14 kg/cm o.

If the lignocellulose material used consists of wood, it is advantageous to first transfer this in cuts.

The nitroanthraquinone compounds can be added to the lignocellulosic material also already during the impregnation.

It can also be advantageous to allow the nitroanthra-quinone compounds to act on the lignocellulosic material in a pre-treatment phase together with the digestion chemicals in the temperature range of approx. 90-150°C so that the lignin content is not significantly reduced, i.e. to a 20% solution, and that possibly a part of the nitroanthraquinone compounds that does not penetrate into the lignocellulosic material can be recovered.

According to the invention, one or more nitroanthraquinone compounds are added during the digestion process. This includes, for example, mono- and/or dinitroanthraquinones which may have one or more additional substituents in addition to the nitro groups. Additional substituents include, for example, alkyl, alkoxy, halogen, amino, hydroxy, carboxy and/or sulfo groups and/or fused iso- or hetrocyclic rings. Preferred as additional substituents are alkyl and alkoxy groups each with 1 to 4 carbon atoms, as well as chlorine and/or sulfo groups. The number of additional substituents can for example be 1 to 6, preferably 1 to 4. Examples of nitroanthraquinone compounds that can be added are: 1- and 2-nitroanthraquinone; 1,5-, 1,6-, lj7-» 1>8-, 2,6- and 2,7-dinitroanthraquinone; 1-nitro-5-, 1-nitro-7-, 1-nitro-8-sulfo-anthraquinone; 1-nitro-4-chloro-5-sulfoanthraquinone; 1-nitro-5-, 1-nitro-6-, 1-nitro-8-, 2-nitro-1-chloroanthraquinone; 2-nitro-4,5-dichloroanthraquinone; 2-nitro-1,4-,1-nitro-5,8-diamino-anthraquinone; 1-nitro-4-amino-anthraquinone; 1,3-dinitro-4-amino-anthraquinone; 1-nitro-4-hydroxyanthraquinone; 1-nitro-3,4, 1-nitro-5,8-, 1,5-dinitro-4,8-dihydroxyanthraquinone; 1,5-dinitro-4,8-dihydroxy-3,7-disulfo-anthraquinone; 1,8-dinitro-4,5-dihydroxyanthraquinone; 1,5-dinitro-2,6-dihydroxy-3,7-disulfo-anthraquinone; 2-nitro-3,4,7-trihydroxy-anthraquinone; 1-nitro-4-ethoxy-anthraquinone; 1-nitro-2-, 2-nitro-3-carboxyanthraquinone; 1-nitro-3-carboxy-4-amino-anthraquinone, 4,4'-dinitro-1,1'-dianthrimide; 1-nitro-4-, 2-nitro-1-methyl-anthraquinone; 1-nitro-4-bromoanthraquinone; l-nitro-3-sulfo-4-bromo-anthraquinone and l-nitro-5-et-oxy-anthraquinone.

It is also possible instead to use nitroanthraquinone compounds or, in addition, the partially hydrogenated derivatives of nitroanthraquinone compounds and/or their automeric forms.

Preferably, 1- and 2-nitroanthraquinone, 1,5-, 1,6-, 1,7-, Ij8-, 2,6- and 2,7-dinitroanthraquinone, 1-nitro-5-chloro-anthraquinone, l- nitro-8-sulfo-anthraquinone, 1-nitro-4-amino-anthraquinone, l-nitro-4-hydroxy-anthraquinone, 1-nitro-2-carboxy-anthraquinone, l-nitro-5-ethoxy-anthraquinone and/or 2-methyl-1-nitro-anthraquinone, especially the above-mentioned dinitro compounds.

The above-mentioned compounds can each time be added

used alone or in desirable mixtures with each other.

Particularly preferred is the addition of mixtures which do not contain further substituted mono- and/or dinitroanthraquinones. Such mixtures can, for example, be obtained by the technical nitration of anthraquinone and/or mononitroanthraquinone. In particular, in the method according to the invention, mixtures of mono- and/or dinitroanthraquinones which are formed when anthraquinone is mono- or dinitrated on a technical scale and/or mononitroanthraquinone mixtures can be used is nitrated and the isomers important as dye intermediates are separated from the resulting products, e.g. 1-nitro-, 1,5- and/or 1,8-dinitro-anthraquinone. The latter mixtures which as essential components may contain e.g. 1,5-, 1,6-, 1,7-, 1,8-, 2,6 and/or 2,7-dinitro-anthraquinone, until now unwanted by-products are formed in the anthraquinone nitration. Particularly preferred mixtures contain, for example, 0 to 3 wt. 1-nitroanthraquinone, 5 to 12 wt.-? 1,5-dinitroanthraquinone, 15 to 35 wt.-? 1,6-dinitroanthraquinone, 15 to 35 wt.-? 1,7-dinitroanthraquinone, 15 to 50 wt.-? 1,8-dinitroanthraquinone, 0.5 to 3 wt-? 2,6-dinitorantrachin-one, and 0.5 to 3 wt-? 2,7-dinitroanthraquinone.

The addition according to the invention of nitroanthra-quinone compounds can for example take place in amounts from 0.001 to 10% by weight, referred to the lignocellulosic materials used. Preferably, 0.01 to 1.0 wt. of the addition referred to lignocellulosic materials.

The method according to the invention has the advantage that it leads to a significant acceleration of the delignification in the soda process. A clear acceleration is also observed in the sulphate process and the polysulphite process. The method according to the invention also has the advantage that hitherto unwanted by-products from the nitration of anthraquinone formed substances and substance mixtures can be added to a technically advantageous utilization.

Depending on the circumstances, the increase in the delignification rate can be used in different ways. A pre-given Kappa number can e.g. is achieved in a shorter time, i.e. the capacity of an already installed cellulose boiler

expands. However, it can also be absorbed at lower maximum boiling temperatures. In both cases, energy is saved. Instead of a shortening of the cooking time and/or a lowering of the maximum cooking temperature, work can also be done with a reduced use of chemicals, which in a known manner (p. Tappi, j)0_(8), p. 400, 1967) have a beneficial effect on the reduced formation of strong-smelling by-products. The way in which these advantages can be utilized optimally in each case depends on the nature of the cellulose manufacturing process used.

In addition to accelerating the delignification, the process according to the invention achieves a stabilizing effect on the cellulose so that for a given Kappa number, the cellulose can be obtained in higher yields.

Example 1

Cuts of fir trees were soaked in a laboratory kettle with a soda-kettle liquor containing 22 ? active alkali (referred to the weight of the wood). The ratio between liquid and wood is 4:1, the initial cooking time 60 minutes, the finished cooking time at 175°C 80 minutes (concentration A). In the same way, a further digestion was carried out (digestion B), where, however, 0.1 wt. (referred to kiln dry wood) of a dinitroanthraquinone mixture of the following composition:

30.7 weight-? 1,8-dinitroanthraquinone

27.1 weight-? 1,6-dinitroanthraquinone

23.0 weight-? 1,7-dinitroanthraquinone

10.0 weight-? 1,5-dinitroanthraquinone

1.1 weight-? 2,7-dinitroanthraquinone

1.0 weight-? 2,6-dinitroanraquinone

0.7 weight-? 1-nitroanthraquinone

6.4 weight-? other nitroanthraquinone derivatives.

The following results were achieved at these gatherings:

Example 2

a) Cuts of fir wood were soaked in a soda-kettle liquor containing 22 ? active alkali (referred to tEee's weight). The ratio between liquid and wood was 4:1, the initial cooking time 60 minutes, the finished cooking time at 175°C 116 minutes. With this addition, the cellulose yield was 51.5 ? with a Kappa number of 67-b) The procedure was as under point a), however, 0.1 wt.-? (referred to oven dry

by) of the dinitroanthraquinone mixture mentioned in example 1. With this digestion, a Kappa number of 67 was achieved already after a final boiling time of 56 minutes at 175°C. The cellulose yield was 53.6 ?.

Example 3

a) The procedure was as in example 2 a).

b) The procedure was as in example 2 b). The yield of 51.5 ? cellulose was already obtained after 86 minutes

finished cooking time at 175°C. The Kappa number stood at 53-

Example 4

a) Cuts of fir wood were subjected to a sulphate digestion in a laboratory cellulose digester. The relationship between

baking soda and wood amounted to 4:1. The boiling liquor contained 17.5 ? effective alkali at a sulphidity of 47%• The initial boiling time was 60 minutes, the final boiling time at 175°C 40 minutes. The cellulose yield was 53.7%, the Kappa number 54.

b) In a further support corresponding to a), the work was carried out under the same conditions. However, it came to be

the cooking lye set 0.1 weight-? (referring to kiln-dried wood) a dinitroanthraquinone mixture of the following composition:

33.0 weight-? 1,6-dinitroanthraquinone

21.7 weight-? 1,8-dinitroanthraquinone

21.6 weight-? 1,7-dinitroanthraquinone

6.5 weight-? 1,5-dinitroanthraquinone

1.9 weight-? 2,6-dinitroanthraquinone

1.8 weight-? 2,7-dinitroanthraquinone

1.4 weight-? 1-nitroanthraquinone

After a final boiling time of 40 minutes at 175°C, a cellulose yield of 52.4 ? with a Kappa number of 46.

Example 5

a) Cuts of fir wood were subjected to digestion using the sulphate method at a ratio of caustic soda to wood of 4:1. The effective alkali, referred to the weight of the wood, was 17.5 ?, the sulphidity 47%. After an initial boiling time of 60 minutes and a final boiling time of 45 minutes at 175°C, a cellulose yield of 52.7 ?, a Kappa number of 48, was obtained.

b) In the event of a further vote, the same approach was taken as point a), however, it was referred to

kiln-dried wood, added 0.1 weight-? of the mixture of dinitroanthraquinones specified in example 4. A Kappa number of 48 was already achieved after 39 minutes of cooking time at 175°C. The cellulose yield was 52.7 ?.

Claims (4)

1. Process for delignification of lignocellulosic materials by digestion of lignocellulosic materials with ordinary cooking liquids, preferably an alkaline cooking liquid, under ordinary cooking conditions in the presence of aromatic nitro compounds, characterized in that one or more nitroanthraquinone compounds are used as aromatic nitro compounds in an amount of 0.01-1 % by weight, referred to lignocellulosic material used. 2. Method according to claim 1, characterized in that the aromatic nitro compound used is 1-nitroanthraquinone, 2-nitroanthraquinone, 1,5-dinitroanthraquinone, 1,6-dinitroantrachninone, 1,7-dinitroanthraquinone, 1,8-dinitroanthraquinone, 2,6-dinitroanthraquinone, 2,7-dinitroanthraquinone, l-nitro-5-chloranthraquinone, l-nitro-8-sulfoanthraquinone, l-nitro-4-aminoanthraquinone, l-nitro-4-hydroxyanthraquinone, l-nitro-2-carboxy- anthraquinone, 1-nitro-5-ethoxyanthraquinone and/or 2-methyl-1-nitroanthraquinone. 3. Method according to claims 1-2, characterized in that the digestion is carried out in a closed reaction vessel at maximum temperatures in the range of 150-200°C over a period of 0.5-480 minutes. 4. Method according to claims 1-3, characterized in that a mixture containing 0-3 wt% 1-nitroanthraquinone, 5-12 wt% 1,5-dinitroanthraquinone, 15-35 wt-% 1,6-dinitroanthraquinone, 15- 35 wt% 1,7-dinitroanthraquinone, 15-50 wt% 1,8-dinitroanthraquinone, 0.5-3 wt% 2nd, 6-dinitroanthraquinone and 0.5-3 wt% 2,7-dinitroanthraquinone .